1. Field of the Invention
This invention relates to an apparatus for electrically operating a circuit breaker in which a spring is compressed by means of a rotating motor and mechanical energy stored within the spring is released to shut off the circuit breaker.
2. Prior Art
One of such apparatuses for electrically operating a circuit breaker is arranged as shown in FIG. 7 to FIG. 10.
The OFF-operation of this apparatus to open the circuit will be described with reference to FIG. 7 to FIG. 10. A frame 3 of a prior art apparatus is secured in front of a circuit breaker 1. An electric motor 4 is secured on the frame 3 and the rotation of the motor 4 is transmitted to a main shaft 6 which drives a ratchet gear 5 via a reduction gear 8. The main shaft 6 is connected to the motor via a one way clutch 7. The ratchet gear 5 is provided with a cam 11, which rotates together with the ratchet 5 in a unitary motion. The can 11 engages with a roller 17 journaled for free rotation on a side wall 12b of a slider 12 for causing the slider 12 to slide. A guide rod 14 is secured to the frame 3. The guide rod 14 extends through a rod insertion hole 15 provided on a front wall 12a of the slider 12.
Thus the slider 12 is guided by the guide rod 14 to slide thereon. A spring 16 is attached to the guide rod 14. The slider 12 is provided with two handle drive pins 13 to drive a handle 2 of the circuit breaker 1.
When an OFF signal is supplied, the motor 4 drives the main shaft 6 in rotation via the ruduction gear 8 and the one way clutch 7, thereby causing the ratchet gear 5 to rotate in a direction of an arrow A in FIG. 7. The can 11 also rotates with the ratchet gear 5 in the direction A, then moves into contact engagement with the roller 17 for causing the slider 12 to slide in a direction of an arrow B. At this time the front wall 12a of the slider 12 compresses the spring 16 as shown in FIG. 8, while also throwing the handle 2 into the OFF-position of the circuit breaker 1 by means of the handle drive pins 13. A stop lever 19 is swingably mounted on the side wall 12b of the slider 12. The side wall 12b is provided with a guide and stopper pin 23 to engage with an elongate hole of the stop lever 19. The stop lever 19 is urged against the side wall 12b by means of a twist spring 20 as shown in FIG. 10. The stopper pin 21 of the cam 11 engages with a bent portion of the stop lever 19 for causing the stop lever 19 to swing against the twist spring 20. Moving in the direction B, the slider 12 moves to a position where the circuit breaker 1 becomes OFF to open the circuit and then the stop lever 19 engages with an actuating lever of a limit switch 18. When the ratchet gear 5 further rotates, the cam 11 causes the stop lever 19 to swing in a direction of an arrow C against the twist spring 20. In this manner, the stop lever 19 actuates the limit switch 18 to stop the motor 4. The stopper pin 23 terminates swinging motion of the stop lever 19 as shown in FIG. 9, so that overrun of the cam 11 is prevented. The slider 12 is held by a latch mechanism 22 at a position shown in FIG. 9. The latch mechanism 22 is to hold both the slider 12 and the spring 15 at a position at which the spring 16 is urged. The latch mechanism 22 is arranged by a link 22a of the slider 12 and a latch (not shown) of the frame 3. Additionally the ratchet gear 5 is provided with a fixed pawl 33 to prevent reverse rotation thereof.
In FIG. 10, operating a manual operation handle 9 in a pumping fashion permits rotation of the ratchet 5 in the direction A shown in FIG. 7. Thus, the off-operation manual of the circuit breaker can be effected in a manner similar to the operation by the motor 4. In the manual mode, the motor 4 is disconnected with the aid of the one way clutch 7.
The ON-operation of this conventional apparatus to open the circuit will now be described with reference to FIG. 9 which shows the OFF state of the circuit breaker. When the latch 22 is actuated upon operation of an ON signal, the slider 12 is set free from being latched and the stored mechanical energy of the compressed spring 16 is released. The slider is then pushed out by the spring 16 to slide in a direction of an arrow D while at the same time the stop lever 19 moves in the direction D, during which the slider 12 throws the handle 2 into ON position by means of the handle drive pins 13 as shown in FIG. 7.
With the conventional apparatus for electrically operating a circuit breaker thus far described, it is necessary to stop the motion of the cam 11 at a specific location so that the cam 11 and the roller 17 are positioned within a predetermined area after the OFF-operation is completed. For this purpose, a special type of brake such as reverse rotation was applied to bring the motor 4 to a stop, or mechanical strength of the bent portion which serves to stop the further swing motion of the stop lever 19 was increased, thereby preventing overrun of the cam 11 due to inertial rotation of the electric motor 4. Also in the case of malfunction of a limit switch 18 which operatively engages with the cam 11 to switch off the motor 4, there have been shortcomings in which the stopper portion of the cam 11 is damaged or the motor 4 burns out due to overload.